Electric valve circuits



Jul 5, 1932.

BOYAJIAN 1,866,343

ELECTRIC VALVE CIRCUITS Filed Dec. 24, 1930 FT l. /2 22 23 24 l4 a z; 20 m l5 @(WWHMHAMWh vvvvvvvv vvvvv AMA Inventor Aram Boyajian b His Attorney.

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My invention relates to electric valve cir-= cuits and more particularly to'such circuits including valves of the t provided with an anode, acathode and a control gr1d,m

5 which the grid normally loses control after current has once started in the valve.

Heretofore, various circuits have been .devised utilizing electric valves of the discontinuous controltype,sucl1, for example, as

30 vapor electric discharge valves, which are particularly advantageous for; many applications loecause of the large amounts of power that they can handleat ordinary operating voltages. By the term discontinuous control electric valves, ll refer to that type of valve provided with an anode, a cathode, and a control grid, in which the starting of current through the valve is determined by the potential upon the control grid, but in which a current flowing through the :valve may be interrupted only by reducing its anode potentiel below the critical value, that is, in which the grid loses control of the conductivity of the valve when current once has been initiated 25 in it. it often becomes desirable to be able to interrupt. the current flowing in the valves at sometime other than that at which-the anode potential is reduced below the critical value which, for a valve of this type, may he so of the order of magnitude of or volts. For example, in the use of such valves in alternating current circuits, it frequently becomes desirable. to interrupt the current flowing in the valves at any predetermined point ole of the alternating potential which in the is applied to the anodes.

It is an ject of my invention, therefore, to provide an electric circuit including a discontinuous control electric valve which will so have the shove-mentioned characteristics, and which will he simple and flexible in operation.

it is a turther object of my invention to provide an alternating current circuit including a discontinuous control electric valve in which the current through the valve may interrupted at any predetermined point in the cycle at alternating potential applied to the anode oi the valve.

In accordance with my invention, 1 conto meet the alternating current circuit to be con man, ssncnusnrrs, I

a carton or w roan trolled'in series with the anode and cathode of a discontinuous control electric valve. The anode and cathode of the valve are also connected in series with a second alternating current circuit, the current in the second circuit having an amplitude substantially equal to or greater than that of the current flowing m the first circuit, and having a frequency which is preferably several times that oi the first circuit. A filter circuit is connected in series with each of the alternating current circuits to prevent the flow of current of one frequency in the circuit of the other frequency. With this arrangement, the current flowing through the valve is periodically reduced to substantially zero at the higher tre= quency, the instantaneous energy required by the low frequency circuit flowing, during this short interval, through the high frequency circuit. Any well known means may be provided for controlling the excitation of the control id to interrupt the current fiowin in the low frequency circuit at any desire, instant, as, for example, by e roviding a phase. shiftin scheme for controing the phase of the gri potential with respect to the anode potential. v

For a better understanding of y inven tion, together with other and further oh jects thereof, reference is had to the follow= ing description taken in connection with the accompanying drawing and its scope will he pointed out in the appended claims. Fig. l ot' the accompanying drawing illustrates my invention as applied to an arrangement tor interrupting the flow of current in an alternating current circuit at any point in the cycle, while Fig. 2 shows certain diagrams to aid in the understanding of my invention.

Referring to Fig. l of the accompanying drawing, l have i1 ustrated an arrangement for controlling the current supplied to a load device 10 from a source oi alternating current 11 through the circuit 12. This arrangement includes a discontinuous control electric valve 18, whose anode and cathode are connected in series with the circuit 12. The valve 13 is rovided with a grid circuit which includes t e secondary winding of a grid transformer it and a current limiting resistor 11% 15. The rima winding of the grid transformer 1 may energized from any suitable source of alternatin potential variable in phase,such, for examp e as the secondary member 16 of a rotary p ase shifting arrangement 17 which is energized directly from the alternatin current source 11 through a phase s littmg circuit comprising a capacitor 18 an reactor 19. In order to u periodically reduce the valve current to substantially zero so that the grid may regain control the anode-cathode circuit of the valve 13 is a so connected in series with a source of alternating current 20, which preferabl u has a frequency several times that of the a ternatin current source 11. A resistor 21 is include in this circuit in order to limit our- I rent flowing through the valve. A filter com prising ca acitor 22 and reactor 23 is con- 3 nected in t e alternating current circuit 12 in order to substantially sup ress current of any frequency other than t at of the alternating current source 11, while a filter comprisin ca acitor 24 and reactor 25 is'con- 85 necte in t e circuit of the higher frequency source in order to suppress the lower frequency current from the circuit 12.

The operation of the above-described apparatus will be more clearl understood by so reference to Fig. 2 in whic curve I represents the alternating current which would normally flow in the circuit 12 if the valve 13 were short-circuited, curve II re resents the alternating current which woul be de- 86 livered b the source 20 and would normally flow in t e circuit were the electric valve 13 short-circuited, and curve III represents the resultant of curves I and II. The solid portion of the curve above the' axis represents the current which actually flows in the valve,

while the dotted portion of the curve below the axis represents the current which wouldflow exce t for the unilateral conductivity of the va ve 13. Obviously this dotted portion of the current may also be passed through the circuit 12 by connectin another valve in parallel to the valve 13, ut with its anode and cathode reversed. The amplitude b of the current represented by curve II is somewhat greater than the amplitude a of the-current represented in curve I so that the resultant of these two currents periodicall passes through zero at the frequency of e source 20. However, in some cases, the grid of the valve 13 may be able to rein control of the current in the valve when 1t is reduced to some small value greater 06 that the current owing throughvthe valve l may be interrupted at any point in the c cle of the current represented in curve II at which the valve current passes through zero. Hence, the accuracy with which the point, at which current is interrupted, may be controlled, increases directly with an increase in the frequency of the current supplied by the alternating current source 20. It will be apparent that the filter circuits 22, 23 and 24, suppress the high uency current from the low frequency circuit, and the low frequency current from the high frequency circuit respectively, although whenever the resultant valve current is less than that flowing in the circuit 12 the instantaneous energy furnished to the load device 10 will flow through the high frequency circuit. In some cases it may be permissible to omit one or both of these filtercircuits.

While I have described what I at present consider the preferred embodiment of my invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from my invention, and I, therefore, aim in the apgended claims to cover-all such changes an modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is v 1. In combination, an alternating current circuit, a discontinuous control electric valve included in said circuit, and means for establishing control of said valve at any predetermined instant within a conducting half cycle of said alternating current comprising a source of periodic current in circuit with said valve, the frequency of said periodic current being substantially greater than that of said alternating current circuit.

2. In combination, a discontinuous control electric valve provided with an anode, a cathode and a control grid, a circuit including a source of alternating current and the anode-cathode circuit of said valve, and means for enabling the control grid to regain control of the valve current at any redetermined instant within a half cycle 0 said alternating current comprising a second cir cuit also including said anode-cathode circuit an? a source of tasltternatlilng current lfilving a y en su antia y greater t an that of it fir circuit.

3. In combination, a discontinuous control electric valve provided with an anode, a cathode and a control grid, a circuit including a source of alternating current and the anode-cathode circuit of said valve, and means for enabling the control grid to regain control of the valve current at any redetermined instant within a half cycle 0 said alternating current comprisin a second circuit alsoincludin said anode-ca ode circuit, and a source of a ternating current havin a frequency substantially greater than tat of Ill said first circuit, and an amplitude such that the resultant current flowin in the two circuits periodically falls be ow the critical value of the valve.

4. In combination, a discontinuous control electric valve provided with an anode, a cathode, and a control grid, a circuit includ ing a source of alternating current and the anode-cathode circuit of said valve, andmeans for enabling the control grid to regain control of the valve current at any redetermined instant within a half cycle 0 said alternating current comprising a second circuit also includin said anode-cathode circuit and a source of a ternating current having a frequency and amplitude greater than the frequency and am litude, respectively, of the current of said rst circuit.

5. In combination, an alternating current circuit, a discontinuous control electric valve included in said circuit, means for establishing control of said valve at any predetermined instant within a conducting half cycle of said alternating current comprising a source of periodic current in circuit with said valve, the frequency of said periodic current being substantially greater than that of said.

alternating current circuit, and means for preventing the flow of current of one frequencly' in the circuit of the other frequency.

6. n combination, a discontinuous control electric valve provided with an anode, a cathode, and a control grid, a circuit including a source of alternating current and the anode-cathode circuit of said valve, a second circuit also includin the anode-cathode circuit of said valve an a source of alternatlng current having a fre uency and amplitude substantially greater t an the frequency and amplitude, respectivel of the current of said first circuit, a filter circuit included in each of said alternating current circuits to substantially suppress the flow of any current therein of the frequency of the other circuit, and a circuit for exciting said control grid. In witness whereof, I have hereunto set my hand this 18th da of December, 1930.

AM BOYAJIAN. 

